1. Field of the Invention
The present invention relates to a method for assigning a radio resource to a mobile station by collecting a radio resource at a constant rate from another mobile station being served by a base station apparatus having a 1xEV-DO system.
2. Background of the Related Art
In general, an IS-95 based mobile communication system provides voice-centered services. Recently, however, thanks to the development of the 1xEV-DO wireless protocol, which is a forward link providing the maximum 2.4576 Mbps high speed packet data service, the mobile communication system is now able to provide multimedia services, such as IMT-2000 service as well as high speed packet data service, moving image service, and further packetized voice service.
The 1xEV-DO system is not focused on providing voice-centered services like IS-95. Rather, it is aiming to provide high speed packet data services only. Specifically, the data source of each mobile station varies depending on the wireless environment. The high speed data in a forward link is first loaded into a time slot that is segmented into 1.67 ms units and is transmitted through time division communication.
Therefore, to process high speed data traffic, the base station apparatus of the 1xEV-DO system needs to be able to increase the data transmission rate in a cell, based on resource capabilities, and to assign forward link resources to users at any time there is a data service request from a mobile station. Particularly, to maintain a designated frame error rate (hereinafter, abbreviated to FER), the base station apparatus sets a limit on the forward link capacity so that the forward link transmits data at a rate less than a maximum data processing capacity within a cell and performs scheduling through scheduling attempts using various types of appropriate methods.
FIG. 1 is a block diagram of a mobile communication system in a related art. Referring to FIG. 1, the mobile communication system manages a mobile station 11 and includes a base station 10, which provides data services. Mobile station 11 requests data services from base station 10 and receives the corresponding data services. Here, the base station manages a plurality of mobile stations 11a through 11c included in a cell.
Base station 10, in order to manage, utilize and assign available resources more efficiently, ranks the services according to the characteristics of a data call requested from mobile station 11a. That is, base station 10 ranks the priority of a mobile station and the service priority. If it turns out that the service grade given to mobile station 11a is higher than the service grade given to other existing mobile stations 11b and 11c that are already in service, base station 10 assigns a radio resource to mobile station 11a first, given that there are sufficient available resources. Based on the radio resources, base station 10 provides data services to the mobile station 11a. 
However, if there are not enough available resources, base station 10 cannot assign proper radio resources, which means that it is not capable of providing a high speed packet data service according to the service grade given to mobile station 11a. As an alternative, base station 10 suspends the data service being provided to a mobile station having a lower service grade than mobile station 11a, such as 11b, among other existing mobile stations 11b and 11c in service, and provides the data service to mobile station 11a instead.
FIG. 2 is a flow chart explaining a method for managing a radio resource in a related art. With reference to FIG. 2, base station 10 receives a new data call from mobile station 11a (S21). Up to this point, mobile station 11a has no way to find out how much available resources are secured in a base station to which it has access.
If there is a data call from mobile station 11a, base station 10 confirms the priority of the mobile station and the priority of a data service (S23). Once the priorities of the mobile station and the data service are determined, base station 10 determines a service grade for mobile station 11a using the priorities (S25).
For example, when a data call from a mobile station is received, the base station first confirms the validity of the mobile station and decides a service priority for the mobile station referring to a database. Usually, the database has all the information about each mobile station. More specifically, information of a subscriber who pays an expensive information fee, information of a subscriber assigned to a particular VIP, information of a subscriber in an emergency situation, and so forth can be stored in the database. In addition, the priority of each different situation is decided in accordance with the standards set by the service providers.
If the data service requested by a mobile station belongs to a specific service designated by the service providers (e.g., a service with a high priority) or a requested data transmission rate of a mobile station is high relative to the system usage efficiency, the priority of the corresponding data service may be relatively high.
Base station 10 determines the presently available resource (S27) and decides whether the available resource could be assigned to mobile station 11a (S29). Here, the available resource means the number of time slots to be assigned to a mobile station in service.
If the presently available resource cannot be assigned to mobile station 11a, base station 10 checks the states of mobile stations 11b and 11c that are currently in service (S31). When the service grade of mobile station 11a turns out to be higher than the service grade of mobile stations 11b and 11c, base station 10 decides whether it is possible to suspend the data service to the mobile stations 11b and 11c that are in service (S33).
Afterwards, base station 10 transmits a suspension message to mobile station 11b (S35), given that the data service is suspendible for the station, and accepts the data service requested from mobile station 11a (S37). Later, base station 10 undertakes a service opening procedure and provides the data service to the mobile station 11a (S39).
If the suspension of the data service to mobile stations 11b and 11c that are in service seems to be impossible at step 33, base station 10 rejects the data service request from mobile station 11a (S41). On the other hand, if the available resource at present can be assigned to mobile station 11a in step 29, base station 10 can carry out the service opening procedure of step 39 directly.
In any case, where the presently available resource cannot be assigned to mobile station 11a in step 29, base station 10 either performs the data service at the available data transmission rate, which may be unsatisfactory to the service grade given to the mobile station, or provides the data service to mobile station 11a at the proper service grade rate after suspending the data transmissions of mobile stations 11b and 11c in service at that moment.
As described above, the 1xEV-DO mobile communication system generates more traffic volume than the traditional voice service-centered mobile communication system, which unfortunately causes problems like handoff and overload many times. Also, to provide prompt service in response to requests from the mobile station having a high service priority (e.g., high quality of service (QoS)), the 1xEV-DO mobile communication system should reserve more resources than the conventional voice service-centered base station.
In short, the base station with the 1xEV-DO system manages the resources to provide the data service requested from the existing mobile station within its cell. Also, the 1xEV-DO system performs the data service through a scheduling process that assigns a radio resource or a band based on the service characteristics of a call requested from the mobile station. Since the resources the base station may assign are limited, the designation of a call and the resource assignment for the quality of service are guaranteed within the limited resources. However, if the resources the base station could assign are not secured, the data service request from the mobile station with a higher service grade, than the data service grade of other mobile stations in service, cannot be met. As a consequence, the data service request from the mobile station with the higher service grade is turned down or the data service provided to the other mobile stations in service should be inevitably suspended to meet the data service request of the mobile station with the higher service grade.
Furthermore, some resources might be reserved in a base station by way of solving the above-described problems. But in such case, the entire system could be degraded.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.